The term "day-crosser" refers to someone who works extremely long hours, often crossing over from one day to the next. There are several synonyms for this term that can be used interchangeably. One common synonym is "all-nighter," which refers to someone who stays up all night working. Another similar term is "night owl," which denotes a person who works late into the night hours. "Workaholic" is another synonym for a day-crosser, indicating someone who is addicted to work and cannot stop themselves from working long hours. Finally, "grinder" is a slang term that also signifies a day-crosser who is dedicated to working hard and achieving success.